Tobacco has been cultured, in the beginnings, as an ornamental and as a medical plant, imposing itself subsequently as an essentially luxury good getting into human culture and modifying human customs and habits.
Tobacco has, amongst the agricultural plants, a position that is not comparable with other plant crops and presents certain peculiarities such as:
1. it is one of the few plants marketed only for its leaves;
2. it is the major non-alimentary plant in the world with a production extension higher than four million hectares in the whole world;
3. in many countries it is a very important instrument for economical and financial politic;
4. its consumption is based on the transformation of the leaves into smoking products, inhaling powders and chewable products;
5. considering its narcotic substance characteristics and its dangerousness for human health, there have always been attempts aimed to forbid its use and hence its production.
The evolution of the Nicotiana genus into different habitats, initially through natural selection and poliploidisation and, later on, through human-driven selection, has brought to the appearance of a vast range of kinds, all selected on the basis of the leaf properties being the leaf considered as the only valuable part of the plant.
Recently, alternative uses of tobacco have been indicated in addition to the above-listed ones:
1. the production of alimentary proteins through purification thereof from leaves (Long R. C. 1979. Tobacco production for protein. Project n. 03245. North Carolina State university, Raleigh N.C.);
2. the extraction of pharmacologically useful active ingredients normally present in the leaves (Baraldi M. et al. 2004. Presenza di sostanze Benzodiazepino-simili in estratti di foglie di tabacco (Nicotiana tabacum). Atti Ist. Sper. Tab., 23 Aprile, Roma, pp. 45-52);
3. the production of recombinant proteins expressed in the leaves or in the seeds of genetically modified plants (Twyman et al. 2003. Molecular farming in plants: host systems and expression technology. Trends Biotechnol. 21:570-578).
The tobacco plant presents a very large leaf area, a small inflorescence and a ratio aerial part:roots that is the highest observed among agricultural plants (Went, 1957. The experimental control of plant growth. pp. 343. Chronica Botanica, Waltham, Mass.).
Taking into account the economic relevance exerted by tobacco's cultivation, notwithstanding the alarming increase of tabagism amongst the youngest, Europe provides grants for its cultivation giving rise to perplexity both of economical and ethical nature.
The European Commission on its internet site (www.ec.europa.eu/agriculture/publi/fact/tobacco) affirms: “there are no economically valid alternatives to this culture that does not use good soils. The incentives to tobacco's culture permits the survival of the rural tissue and produces an industrial activity that contributes to the survival of regions menaced by desertification”.
The negative consequences, in environmental terms, of the use of fossil combustibles and the limited availability of petroleum, require the search of new energetic sources. Amongst these, biofuels are the best choice in a future perspective due to their renewability.
Considering bio fuels of agricultural origin, up to date, the attention has focused on the production of bioethanol starting form simple (i.e. saccharose) or complex (i.e. cellulose) sugar producing plants. Model plants for such production has been identified in sugar cane, corn, wheat, potato, tapioca, sugar beet, barley, sorghum etc. The development of cultures aiming to the maximisation of the production of biomass to be transformed in ethanol through fermentation processes or for the production of biofuels or gas through gasification may have the same scope. Alternatively, the state of the art aims to the production of fuel oil and biodiesel starting form oleaginous or non oleaginous species but rich in oil such as soybean, sunflower, rape, peanut, flax, corn, sesame, palm, palm-kernel, coconut, ricinus etc.
The choice of the ideal species for the production of biofuels shall relate on the fulfilment of requirements such as:
1. determining a net energetic gain in the difference between culture's input and output, comprising in the said calculation the energetic costs for the production of the agricultural machinery and for the processing for the extraction and transformation/purification of the oil;
2. determining environmental benefits deriving from the supportability of the agricultural production, decrease of the CO2 and particulate matter (e.g. PM-10) emission after combustion and limited use of agrochemicals such as pesticides herbicides and fertilizers;
3. being economically competitive and, possibly, determining social benefits that may increase the system's economy, e.g. by lowering indirect costs on the sanitary system, considering also that the fossil energy used at presents imposes environmental costs that are usually not in the cost determination; a bio fuel shall envisage benefits both on the cost competitiveness side and on the environmental side;
4. being available in large quantities without decreasing the alimentary availability; the use of agricultural plants traditionally used for food production does not reasonably allow their use for the production of bio fuels without determining a reduction of the food sources deriving from said plants hence increasing the costs of the raw materials;
5. the plant culture from which it derives shall possibly concern marginal lands that are not likely to be used for alternative cultures.
In the state of the art the plants taken into account for oil production are: soybean (Glycine max), sunflower (Helianthus annuus), rape (Brassica napus), peanut (Arachis hypogaea), ricinus (Ricinus communis), flax (Linum usitatissimum), corn (Zea mais), sesamus (Sesamum indicum), palm (fruit, Aracaceae), palm-kernel (seed, Aracaceae), copra (coconut, Cocos nucifera), safflower (Carthamus tinctorius), olive (Olea europea), cotton (Gossypium sp.), acajou (Anacardium occidentale), hemp (Cannabis sativa), poppy (Papavers sp.), mustard (Brassica sp.), grape (Vitis sp.), apricot (Prunus armeniaca), pine (Pinus sp.), argan (Argania spinosa), avocado (Persea americana), almond (Prunus amygdalus), hazelnut (Corylus avellana), nut (Juglans regia), neem (Azadirachfa indica), niger (Guizotia abyssinica), jojoba (Simmondsia chinensis), rice (Oryza sativa), pumpkin (Cucurbita sp.), crambe (Crambe abyssinica).
On the contrary, in the prior art, tobacco has always been considered as an agricultural plant apt for the production of leaves.
The only three publications in literature, listed below, suggesting further uses for tobacco, take into account the present tobacco varieties, that have been selected for the production of leaves, as a source of the seed by-product for oil extraction.
In particular Giannelos et al. (Tobacco seed oil as an alternative diesel fuel: physical and chemical properties. Industrial Crops and Products, 2002, 16:1-9) declaring that “the seed is a by-product of the leaf production in Greece” suggest the possibility of using said seeds for the production of fuels describing methods for the extraction of oil form tobacco seeds that uses solvents, indicating, however, that the oil extracted from tobacco may not be used as such as biodiesel due the high iodine value in it.
Usta N. (Use of tobacco seed oil methyl ester in a turbocharged indirect injection diesel engine. Biomass and Bio-energy, 2005, 28:77-86) declares that tobacco seed oil is a by-product of the world production of leaves, estimates the worldwide production of seed deriving from tobacco's cultivation for leaves and describes the oil extraction from seed through the use of solvents.
Finally, Patel et al. (Production potential and quality aspects of tobacco seed oil. Tobacco Research, 1998, 24:44-49) estimate the production of tobacco seed as a by-product of leaves in India equal to 1,171 kg/ha with a content of oil of the 38% by weight and describe its extraction by the use of solvents.
The technological processes for oil extraction comprise mechanical (pressure) and chemical (solvents) techniques. In practice, the two systems are often combined. In general the mechanical extraction is carried out on seeds containing more than 20% of fat material (e.g. rape and sunflower) wherein the seeds dimensions are favourable for the pressing technique. Tobacco seed, by way of example, due to its very tiny dimensions, is subject to oil extraction by chemical treatments.
Generally, the possibility of extracting oil mechanically, facilitates the direct extraction in the seed production sites, hence also at the farm's level, with small plants.
For lower quantities of fat material chemical extraction is used, and can be applied also to the oilcake, leftover of the mechanical extraction, in order to recover the remaining 6-12% of oil left after the mechanical treatment. The oils extracted by the use of solvents (e.g. hexane) prior to commercialisation for alimentary uses, require a refinement step. The main product of the extraction process is crude oil; the mechanical extraction further produces the protein oilcake whereas the chemical one produces flour. The latter, used in animal feeding, weights in a critical way upon the production and processing of oily seeds economy.
In certain cases the production is bound to the protein flour request (e.g. soybean). The crude oil may subsequently be rectified with a series of physicochemical treatments (e.g. pH adjustment, filtration, degumming, discolouration, etc.) depending on the intended use.
The mass balance of the entire process varies from species to species, by way of example considering a content in oil of 42% for the sunflower seeds, for a ton of seeds (that are the main product) 2.6 by-product (biomass) tons are considered, with a production of 420 kgs of crude oil, 580 kgs of oilcake, obtaining a final production of 390 kgs of refined oil and 30 kgs of process residuals. Taking into account that the average yield of sunflower seeds is about 2.6 t/ha (+/−15%) it can be calculated that the yield/hectare of oil is equal to about one ton. This relation is valid also for other species, in particular for rape, depending on the percentage in oil. Vegetable oils may be used directly as fuel oils for heat production (ovens or boilers) or mechanic energy production (engines), utilizing their gross calorific value that is about 8,500 kcal/kg or, after transesterification, transformed as biodiesel.
The use of vegetable oils in boilers may be carried out with conventional burners by substituting the industrial or the heating diesel oil with vegetable oil. This kind of solution appears quite interesting due to the fact that: (i) the price of substituted fossil fuel is often quite similar to the one of the automotive diesel oil and is subject to high excise duties; (ii) the use of oil in boilers requires the organisation of a very simple agroenergetic thread that can end directly in the rural environment, where the fuel producers and the fuel users can be located very near to each other or can even correspond. The higher or lower easiness of the oil extraction process is another important aspect to take into account when an local use of the bio fuel is envisaged. The production economy and the more or less favourable energetic balance will depend mainly on the production per hectare of fuel oil.
The use of vegetable oils in diesel engines requires, on the other hand, a chemical process of transesterification with methanol and a certain fatty acid composition, which may be summarised in a iodine value that has to be equal or lower than 120. Vegetable oils are also often used for alimentary scopes. Depending on the plant, the productions can be mainly directed to alimentary or energetic scopes, or both.
On the light of the above mentioned problems, it would be highly desirable to recycle tobacco's industry for ecological scopes and harmless for human beings.
The identification of an alternative and economically valid use of tobacco does hence constitute a clear worldwide economically interesting topic.